Summer of `(MU)69 Marc W. Buie Southwest Research Institute + Many, many more

2017 Occultations 2017 June 3 2017 July 10 2017 July 17 ● South America and Africa Faint, g’=15.3 – – 2017 July 10 ● – Pacific Faint, g’=15.6 2017 July 17 ● Southern South America Bright, g’=12.6 – –

Deployment MU20170603 ● 13 systems to South Africa near Cape Town 12 systems to Argentina near Mendoza – – MU20170710 ● – SOFIA No mobile ground stations – MU20170717 ● – 25 systems to Argentina near Comodoro Rivadavia

Ground track uncertainties 34 km = 1 mas Ground track uncertainties may25a → last orbit before June 3 ● – HST data through May 25 lc1g2 → last orbit before July 10/17 ● – HST data through July 4 rf3a → current provisional orbit ● – Includes Aug 2017 HST data and July 17 occultation may25a lc1gr rf3a Event x-track [mas] in-track [mas] June 3 1.449 2.172 0.420 0.768 0.240 0.882 July 10 1.520 2.073 0.447 0.582 0.260 0.241 July 17 1.536 2.102 0.464 0.697 0.283 0.254

June 3 occultation goals Detect or eliminate large and dark case for 2014MU69 (D=40 km) ● <3% chance of a null result Only one continent required – Good size result if D=20 km ● 3% chance of a null result is a practical floor Both continents required Harder to detect due to shorter chords and signals – – – Search for extra material around 2014MU69 ● – Optically thick, narrow rings Diffuse material, search region within 30,000 km of central body Some important values to keep in mind ● – Geocentric target distance = 43.3 AU 31,400 km/arcsec, 31.4 km/mas, 1 km = 32 μas Star position (Gaia DR2) good to 100 μas Cross-track error 44 km, timing error 3.3 sec (1σ) –

June 3 deployment and result 22 portable 40-cm telescopes, CMOS detector with GPS timestamps ● – R=14.6, 2 Hz sampling rate, SNR~5, max chord length = 2s 3 portables from UVa South America (12 in Argentina) and Africa (10+3 in South Africa) One telescope broke in shipment to Cape Town ● ● ● – mirror came loose from mount used for spares to fix other systems – Weather good for Argentina Weather turned in western South Africa ● ● – 6 teams drove east to get away from clouds 24 stations collected data at desired time ● – One station strongly affected by clouds but not wiped out No diffuse material or solid body signatures seen in data ●

June 3 picket fence

July 10 occultation goals Search for diffuse or ring material ● – ±30,000 km for stability region = 45 minutes Probe as close to the solid body as possible ● – Solid body event would be a bonus result Target within 1-2 km and 1 sec of predicted path –

SOFIA flight path

July 10 preliminary results No diffuse material or rings seen No obvious solid body signature seen Aircraft got to the requested location and time within requested bounds ● ● ●

July 17 occultation goals Strike-out? Or, third time’s charm Solid-body event a top priority Cover larger uncertainty range – ● ● ●

July 17 deployment Coverage of ~4.5σ (~100 km) Spacing was ~4-5 km Centerline passed over Comodoro Rivadavia ● ● ● – 5 chords Longest was ~1 sec Shortest was ~0.3 sec – – Shape is not simple ●

July 17 results Centerline passed over Comodoro Rivadavia ● – 5 chords Longest was ~1 sec Shortest was ~0.3 sec – – Cross-track error was reasonable In-track error is larger than it should be Shape is not simple ● ● ●

July 17 data

Shape interpretation Single object Contact binary Close binary ● – 34x20 km, very irregular in shape Contact binary ● – 34x19 km Close binary ● D1=20 km D2=16 km – –

Open Questions Explain the June 3 miss Explain the July 10 miss Explain the tension between HST and occultation astrometry ● ● ●

What’s Next? MU20180804? ●

South America

South America